Conventionally, when an electronic circuit board or the like is to be produced, a nickel film is formed on the surface of a base to form a nickel circuit pattern thereon. For example, in order to form such a metal film, some film formation techniques have been proposed, forming a metal film on the surface of a semiconductor substrate made of Si or the like by plating processing such as electroless plating processing, or forming a metal film by PVD, such as sputtering.
When plating processing such as electroless plating processing is performed, however, this requires washing with water after the plating processing, as well as disposing of a waste liquid after the washing. When a film is formed on the surface of a base by PVD such as sputtering, internal stress is generated in the metal film formed, and so there is a limit in increasing the thickness of the film. In particular, in the case of sputtering, a film may be formed only in a high vacuum in some cases.
In view of the foregoing, a film formation apparatus 9 of a metal film has been proposed, for example, as shown in FIG. 6(a), including an anode 91, a base B serving as a cathode, a solid electrolyte membrane 93 disposed between the anode 91 and the base (cathode) B, and a power supply unit 94 that applies voltage between the anode 91 and the base B (see Patent Literature 1, for example).
The anode 91 of the film formation apparatus 9 as stated above is a porous body letting metal ions pass therethrough. Since the anode 91 is such a porous body, solution L including metal ions is allowed to pass through the anode 91 during film formation so as to always supply the metal ions to the solid electrolyte membrane 93. Further, the film formation apparatus 9 includes a pressure unit 96 to press the solid electrolyte membrane 93 against the base B via the anode 91. In this way, a metal film made of metal deposited via the solid electrolyte membrane 93 can be formed on the surface of the base B placed on a mounting base 92.